Punch



W. J. EHRSAM Dec. 5, 1939.

PUNCH INVENTOR. c]. qgmiam. 7

Filed Aug. 8, 1938 ji'm'm Patented Dec. 5, 1939 PATENT OFFICE William J. Ehrsam, Enterprise, Rana, assignor to The J. B. Ehrsam & Sons Manufacturing Com- P y, Enterprise, Kansas Kansq a corporation of Application AugustS, 1938, Serial No. 223,641"

Claims. (Cl. 16485) The present application relates to a punch and a die for'cooperation therewith; and more speciflcally to a punch and die particularly adapted for use in perforating unset plaster board.

a A great deal of perforated plaster board, commonly known as plaster lath, is used in building, as a substituted for wood or metal lath; and it has been found that it is desirable, if not absolutely necessary, to form such plaster board with perforations, of suitable size and spacing, through which the plaster prortudes to form anchorages whereby the plaster is held in place. Such board is customarily formed by spreading a plastic material, usually having a plaster of Paris base, between two layers of paper, or the like; and allowing the plastic to set. In the prior commercial art, it has been customary to cut the board into sections before the plastic has set, thereafter allowing the plastic to set and .then drying the board sections by passing them to and through a dryer in which the excess moisture is removed. After the board has been dried, the boards are stacked into bundles and the desired perforations thermore it has 'been found in the practical art that, whereas the above-described operation produces cleanperforations through some of the boards of the stack, it will form ra ed, rough perforations through others, notably the boards toward the middle of the stack.

It is the primary object of the present invention to provide a punch and die of such character as to permit perforation of plaster board before the plastic has become set, to produce clean, smooth perforations, andto eliminate the production of powderedmaterial. It is a further object of the invention to provide such a'punch and die in order to make possible perforation of the product before the plastic has set,'whereby the drying operation will be facilitated and rendered less expensive. Obviously, if the material is perforated before the plastic has been dried, the drying air will be permitted to come into contact with an enormously increased surface of plastic, whereby the drying and setting step is performed much more rapidly. Although the punch of the present application is primarily intended for use inthe manner above described, it will be obviousthat many of the advantages resulting from the particular construction of my punch and die will arise no used. c

Heretofore, attempts have been made to perforate plaster board by punching prior to the set ting of the plastic, but such attempts have,'to the matter with what material they are best of my knowledge, invariably resulted in failure. Numerous patents have been granted upon machines including punches carried by rotating elements driven at a lineal speed equivalent to the speed of movement of the board in the forming machine; but in practical operation, it was found that such punches invariably produced ragged, imperfect perforations. It is my opinion that the failure of such machines was due in part toan incorrect theory as to the proper method of op-= eration, and in part to the fact that the punches and dies used insuch prior art machines were improperly formed to perform the desired func-' tions in a satisfactory manner.

Further objects of the invention will appear as the description proceeds. To the accomplishment of the above and related objects, my invention may be embodied in the forms illustrated in the accompanying drawing, attention being called to the. fact-however, that the drawing is illustrative only, and that change may be made in the specific constructions illustrated and described, so long as the scope of the appended claims is not violated. Fig. 1 is an elevation of a punch constructed in accordance with the present invention, parts being broken away for clarity of illustration;

Fig. 2 is an elevation of one form of die which may desirably be used in conjunction with such punching machine, showing my punch and anshank ll, an enlarged portion l2, merging with said shank throughatapered shoulder l3, and a. further enlarged portion ll merging with the portion I! through a tapered shoulder l5.

In the leading end or the shank II is romeo asubstantially hemisphericalcavity I6, the depth of which, in an axial direction, is'substantially equal to the diameter of the shank II. A perimetral series of teeth I1 is, arranged about the mouth of the'cavity l6, said teeth being, as is cleary shown in Fig. l, in elevationyshaped substantially as isosceles triangles. The equal sides 13 of such triangle are sharpened to cutting edges; and, as is further shown in Fig. 1, each tooth de- 5 creases progressively in radial thickness from its base I! to sharpness at its apex 20. Thus, when the punch is advanced into a board, the apices 23 of the teeth I! prick into the material like.

needles, and thereafter the sharpened edges [8 1 slice through the material like knives witha shearing action.

cavity l8, and is carried through the material and through the cooperative die. A port 2! opens 1 from the base of the cavity it through the trailing end 22 of the punch. While I have stated that the shankll of the punch III is cylindrical, it will be obvious that it may be of any desired cross sectional shape. 59 While I have furtherstated that the cavity I6 is substantially hemispherical, it will likewise be obvious that that shape is not essential. The

essentials of the cavity are that it shall be so shaped that the inner surfaces of the teeth I1 tinue the-cavity, upon its maximum diameter,

through the length of the punch, whereby slugs punched from the board material would collect and move progressively upwardly through the punch, ultimately being discharged from the 40 upper end thereof. In that case, of course, the header 23, hereafter to be described, would not be necessary. I prefer, however, the illustrated structure; since it is possible that the slugs punched from the board material and retained 5 within the punch, in the manner Just described, might plug the punch passage upon setting, to cause considerable trouble. 1

As is more particularly shown in Fig. 3, th punch is carried by a reciprocable head H with go which is associated a header 23 which is connected to a suitable source of compressed air. The head H carries a spud 24 formed with a port 25 providing communication between the header 23 and the port 2|; and the punch I0 is aflixed 55 to the spud throughthe medium of a coupling 26. Thus, when the perforation has been formed, compressed air will besupplied to the header 23 to flow through the passages 25 and 2| to expel the retained slug of material cut from the board so and retained in the cavity I.

A table 21 associated with the head H is formed with a socket 28' for the reception of the flange 2! of a die 30, said die being secured in place on the table by a nut- 3l, or the like. The die 30 is 55 formed with an opening 32' adapted to receive the shank ll of the punch Ill, with a working lit; said opening 32 communicating with an enlarged passage 33 extending entirely through the die 30.

, Preferably, a stripper plate 34, formed with a 7 port 35 therein, is associated with the other eleshown'in Fig. 3, the board to be perforated con- The portion of the material punched out by the punch is received within the sists of two' layers 31 and 33 of paper or other fibrous material holding therebetween a layer 33 of plastic material.

In Fig. 2 is shown another form of die, indicated generally by the reference numeral 33'. 5 The die 30' is formed with an axial opening 32' which is bordered, at the uppermost end of the die, by an upstanding perimetral ridge ll. Said ridge, in cross section, is shaped 'as a right triangle the base ll of which lies in the uppermost 19 surface of the die, the altitude 42 of which coincides with the internal surface of the opening 32, and the hypotenuse 43 of which lies in a radial plane of the die. Said ridge III is formed with a series of perimetrally spaced, axially extending, substantially V-shaped notches 44, and with a second series of perimetrally spaced, axially extending, substantially V-shaped notches 45 of less depth, each of. the notches I! being positioned substantially midway between two of the notches L For some purposes, Ihave found the die 33' to be more satisfactory. than any other die; partially for the reason that it forms a countersink at that end of the perforation which, during the perforating step, is downwardly presented. That countersink, when it is used at the, back of the plaster lath, tends to forma better anchorage for the plaster applied to the opposite surface of the board.

The die all" shown in mg. 4 is identical with i the die 30, except for the fact that it is formed with teeth 48 arranged about the mouth of the opening 32".

At various points in the specification, and in the claims, I have referred to *unset" plaster .board or plastic. That term is intended to apply subsequent to the initial set and prior to final set.

The condition of initial set is that condition in which a depression, indentation, or perforation formed in the plastic will not be refilled by flow of the material.

I claim as my invention:

l. A punch for perforating unset plaster board or the like, comprising a shank formed at its leading and with a perimetral series of teeth, each of said teeth having its external surface flush with the external surface of said shank being substantially triangular in elevation and the thickness thereof being progressively reduced from the base of the triangle to the apex thereof.

2. A punch for perforating unset plaster board or the like, comprising a shank formed at its leading end with a perimetral series of teeth, each of said -teeth being shaped, in elevation, 40 substantially as an isosceles triangle, the equal sides thereof 'being sharpened to cutting edges, and the thickness of each tooth being'progressively reduced from its innensurface outwardly from the base of the triangle to sharpness at the 5 apex thereof.

3. The combination with apunch formed at its leading end with a cavity and provided with a perimetral series of teeth arranged about the mouth of said cavity, -of a die formed with an 7 opening adapted to receive said punch with a working clearance and communicating with an enlarged passage extending entirely through said die.

4. The combination with a punch formed at u s eaves a perimetral series of teeth arranged about the its leading end with a cavity and rovided with a perimetraiseries of teeth. arranged about the mouth of said cavity and provided with .a port leading from said cavity through the trailing end of said punch, of a die formed with an opening adapted to receive saidpunch with a working clearance and communicatingwith an enlarged passage extending entirely through sai die.

5. The combination with a punch formed at its leading end with a cavity and provided with a perimetral series of teeth arranged about the mouth of said cavity, of a die formed with an opening adapted'to receive said punch with a working clearance, said die being provided with a perimetral series of teeth arranged about said opening and presented toward said punch.

6. The combination with a punch formed at its leading end with a cavity and provided with.

a perimetral series of teeth arranged about-the mouth of said cavity, of a die" formed with an opening adapted to receive said punch with a working clearance, said die being provided with a perimetral series of teeth arranged about said opening and presented toward said punch, the

teeth of said die having axial and peri netral dimensions less than those 'of the teeth on said punch.

7.-"I'he combination with a punch formed at its leading end with a cavity and provided with a perimetral series of teeth arranged about the mouth of said cavity, of a die formed with an opening adapted to receive said punch with-a working clearance, and an axially-extending perimetrai ridge closely surrounding the mouth of said opening and projecting toward said punch, said ridge being formed, in cross section, substantially as a right triangle with its base disposed in the uppermost surface of said die, its altitude coinciding with the. internal surface of said opening, and its hypotenuse lying in a.

' radial plane of said die, the uppermost surface of said ridge, lying in the apex of such triangle, being serrated to form a perimetrai series of teeth. v

.8. The combination with a punch formed at its leading end with a cavity and provided with mouth of said cavity, of a die formed with an opening adapted to receive said punch with a working clearance,- and an axially ,extending perimetral ridge closely surrounding the mouth of said opening and projecting toward said punch, said ridge being formed,-in cross section, substantially as a right triangle with its base disposed in the uppermost surface of said die, it's altitude coinciding with the internal surface of said opening, and its hypotenuse lying in a radial plane of said die, the uppermost surface of said ridge, lying in the apex of such triangle,

being formed with a series of perimetrally spaced, axially extending, substantially v-shaped notches and with a. second series of perimetrally spaced, axially-extending, substantially V-shaped notches of less axial depth, each notch of said second series being positioned substantially midway between two adjacent notches of said first series. Y

9. A punch for perforating unset plaster board or the like, comprising a cylindrical shank formed, at its leading end, with a substantially hemispherical cavity, the volume of said cavity being at least equal to the volumeof a piece of the material to be operated upon having a thickness equal to the thickness of such material and a cross sectional area equal to the cross sectional area of the mouth of said cavity, the mouth of said cavity being supplied with a perimetral series of teeth, each of said teeth having its face flush with the outer surface of said shank,

and its inner surface progressively flaring upon the arcof a circle from the extremity of the tooth toward its root. 7 v

' WILLIAM J.

' entire outer surface flush with the outer surface 

